Sulfonic acid-functionalized carbon coated red mud as an efficient catalyst for the direct production of 5-HMF from D-glucose under microwave irradiation

Though suitable for the fructose conversion to 5-hydroxymethylfurfural (5-HMF), sulfonated carbon catalysts are inefficient for the direct glucose transformation to 5-HMF due to the lack of appropriate Lewis acids. Here, we have reported an efficient and inexpensive catalyst by suitably modifying red mud (RM), a by-product from the aluminum industry. The AD-1:1/SO3H catalyst produced by the acid (HCl) treatment, carbon coating, and SO3H grafting on RM exhibited enhanced surface area, mesoporous characteristics, and suitable Lewis and Bronsted acid sites. The XRD, FTIR, and XPS analysis suggested Fe-2(SO4)(3), Fe2O3, and various carbon functionalities as the major active components in the AD-1:1/SO3H catalyst. The NH3-TPD analysis revealed an appreciable acid site density of 6.8 mmol g(-1). Under microwave heating at 180 degrees C, 30 min, and 90:10 DMSO/water weight percentage ratio, the catalyst produced a D-glucose conversion and 5-HMF yield of 93.05 % and 51.5 %, respectively.